Ideal Gas Thermodynamic Functions For NO From the Total Partition Sum and Its Moments

Abstract

The total internal partition sum, Qint(T), and the translational partition sum, Qtrans(T), were computed for six isotopologues of NO: 14N16O, 15N16O, 14N18O, 14N17O, 15N18O, 15N17O. These were used to determine the total partition sum, Q(T), and its first and second moments, Q̃′T and Q̃″T. The total internal partition sum was computed using term values determined by Qu et al. [Mon. Not. R. Astron. Soc. 504, 5768–5777 (2021)] for 14N16O and those of Wong et al. [Mon. Not. R. Astron. Soc. 470, 882–897, (2017)] for the other isotopologues. These term values are the best available and hence provide the most accurate total internal partition sums and its first and second moments. The uncertainties in Qint(T), its moments, and the resulting thermodynamic functions were determined from the uncertainty in the term values and the uncertainty due to the convergence of the partition sum and its moments. From these quantities, the isobaric heat capacity, Helmholtz energy, entropy, enthalpy, Gibbs function, and the JANAF functions hef and gef, and their uncertainties, were computed on a 1 K grid from 1 to 9000 K. The data are compared with the literature values. The resulting thermodynamic quantities are the most accurate determined from direct summation of Q(T), Q̃′T, and Q̃″T.